Astronomers discover best locations for alcohol in space

Astronomers found what may be the "sweet spot" for methanol production in …

Before everyone starts chanting “interstellar bar crawl!”, I should clarify: the alcohol is methanol (CH3OH, also known as methyl alcohol), which is toxic and not to be confused with its more entertaining cousin ethanol (C2H5OH).

Finding methanol in space is slightly less exciting, perhaps, but only slightly. The purpose of the study is to find the locations under which methanol is produced, because that will help scientists understand how complex organic molecules necessary for life are created in space. So some researchers attempted to determine the conditions under which methanol is produced in interstellar clouds and the envelopes of young stars.

Now, many of you with a bio/chemistry background may be thinking “Methanol? Methanol isn’t a complex organic molecule, it’s just a simple alcohol—one hydroxyl (OH) away from methane.” You would be right, for the most part. But, according to the lead researcher of the project, Douglas Whittet of RPI (the team also includes scientists from NASA Ames, SETI, and OSU), “Methanol formation is the major chemical pathway to complex organic molecules in interstellar space.”

Methanol is formed when carbon monoxide (CO) that is sitting on interstellar dust particles reacts with hydrogen (H2) at low temperatures (very cold—around 10-15 K). For the chemists in the room, H combines with CO to form HCO, which in turn combines with another H to form formaldehyde (H2CO). Add a couple more hydrogen atoms, and you’ve got methanol. Once the methanol is formed, cosmic rays, UV radiation, or small amounts of heat can trigger reactions that combine it to form more complex molecules. All these molecules, in turn, might end up in the disk of dust and gases surrounding a new star and eventually become incorporated into planets.

This study doesn’t actually present new observational data, but involves a new analysis of existing work. The previous measurements looked at wavelengths in the infrared range, where different chemical species (like methanol, water, and carbon monoxide) vibrate. Methanol in particular vibrates at energies that correspond to several wavelengths—one for each of the different molecular bonds. But two, 3.54 μm and 9.75 μm, are the easiest to observe and therefore the most commonly used.

The team looked at data from two regions: interstellar molecular clouds and the envelope regions of young stars (the next step in stellar evolution after molecular clouds). They found that around some of the young stars, about 10 percent, contain higher-than-average quantities of methanol—up to about 30 percent of the total ice (the remainder of which is primarily water, carbon monoxide, and carbon dioxide). Others have so little methanol that it’s barely detectable.

The team also found, for the first time, small concentrations (a few percent) of methanol in cold molecular clouds. Methanol production appears to happen in the coldest, most dense regions of the clouds, where the carbon monoxide is almost "shielded" from becoming carbon dioxide (which is a dead-end pathway) instead of methanol.

They found what may be a "sweet spot" for methanol production: when carbon monoxide builds up at just the right speed on the dust particles, based on the temperature and density of the local conditions. If this rate is too fast, the molecules are buried and can’t react to form methanol; if it’s too slow, the hydrogen reacts with other species and less methanol is produced.

Interestingly, our star might not have had these just-right conditions (yet we are still here!). The abundance of methanol in comets from our own solar system—about five percent of the ice—is on the low end. This means that some other solar systems might have the potential to form more complex molecules (or do so faster) than ours. Either way, this study helps improve our understanding of the conditions that lead to molecules necessary to support life.

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Kyle Niemeyer
Kyle is a science writer for Ars Technica. He is a postdoctoral scholar at Oregon State University and has a Ph.D. in mechanical engineering from Case Western Reserve University. Kyle's research focuses on combustion modeling. Emailkyleniemeyer.ars@gmail.com//Twitter@kyle_niemeyer